8.4 Using Runtime Functions and Predefined Exceptions

The standard header <exception> provides the classes and exception-related functions specified in the
C++ standard. You can access this header only when compiling in standard mode
(compiler default mode, or with option -compat=5). The following excerpt shows the <exception> header file
declarations.

The standard class exception is the base class for all exceptions thrown by
selected language constructs or by the C++ standard library. An object of type
exception can be constructed, copied, and destroyed without generating an exception. The virtual
member function what() returns a character string that describes the exception.

For compatibility with exceptions as used in C++ release 4.2, the header
<exception.h> is also provided for use in standard mode. This header allows for
a transition to standard C++ code and contains declarations that are not part
of standard C++. Update your code to follow the C++ standard (using <exception>
instead of <exception.h>) as development schedules permit.